Limited play data storage media and method for limiting access to data thereon

ABSTRACT

The present disclosure relates to a limited play optical storage media and a method for limiting access to data thereon. This storage media comprises: an optically transparent substrate; a reflective layer; an oxygen penetrable UV coating disposed on a side of the substrate opposite the reflective layer; and a reactive layer disposed between the UV coating and the substrate, the optical storage media having an initial percent reflectivity of about 50% or greater and a subsequent percent reflectivity of about 45% or less.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application is a continuation of U.S. patent applicationSer. No. 09/681,288 filed Mar. 14, 2001.

BACKGROUND OF THE INVENTION

[0002] Optical, magnetic and magneto-optic media are primary sources ofhigh performance storage technology which enables high storage capacitycoupled with a reasonable price per megabyte of storage. Use of opticalmedia has become widespread in audio, video, and computer dataapplications in such formats as compact disk (CD), digital versatiledisk (DVD) including multi-layer structures like DVD-5, DVD-9, andmulti-sided formats such as DVD-10, and DVD-18, magneto-optical disk(MO), and other write-once and re-writable formats such as CD-R, CD-RW,DVD-R, DVD-RW, DVD+RW, DVD-RAM, and the like, hereinafter collectively“data storage media”. In these formats, data are encoded onto asubstrate into a digital data series. In pre-recorded media, such as CD,the data are typically pits and grooves formed on the surface of aplastic substrate through a method such as injection molding, stampingor the like.

[0003] In recordable media, the data are encoded by laser, whichilluminates an active data layer that undergoes a phase change, thusproducing a series of highly-reflecting or non-reflective regions makingup the data stream. In these formats, a laser beam first travels througha plastic substrate before reaching the data layer. At the data layer,the beam is either reflected or not, in accordance with the encodeddata. The laser light then travels back through the plastic and into anoptical detector system where the data are interpreted.

[0004] In some applications, it is desirable to have a limited life foran optical disc. For example, sample computer programs are provided topotential customers in order to entice them to purchase the software.The programs are intended to be used for a limited period of time.Additionally, music and movies are currently rented for a limited timeperiod. In each of these applications and others, when that time hasexpired, the disc must be returned. A need exists for machine-readableoptical discs that do not need to be returned at the end of a rentalperiod. Limited-play discs provide a solution to this problem.

[0005] Limited play discs have been produced in various fashions. Onemethod comprised forming a disc where the reflective layer is protectedwith a porous layer such that the reflective layer becomes oxidized overa pre-determined period of time. Once the reflective layer attains acertain level of oxidation, the disc is no longer readable. The problemwith this and other limited play techniques is that these techniques aredefeatable.

[0006] If the method for providing limited play to optical discs can beeasily defeated by a customer or a cottage industry, discs would nolonger be “limited-play”. In the case of a coating or material renderingan optical disc unplayable, for example, facile removal or modificationof that coating and/or material could provide a disc with unlimitedplayability.

[0007] There is a great desire on the part of movie studios to protecttheir intellectual property. Commercialization of limited-play datastorage media that can be easily defeated to afford data storage mediawith unlimited playability would present an unacceptable risk of losingintellectual property.

BRIEF SUMMARY OF THE INVENTION

[0008] The present disclosure relates to limited play storage media andmethods for limiting access to data thereon. This storage mediacomprises: an optically transparent substrate; a reflective layer; anoxygen penetrable UV coating disposed on a side of the substrateopposite the reflective layer; and a reactive layer disposed between theUV coating and the substrate, the optical storage media having aninitial percent reflectivity of about 50% or greater and a subsequentpercent reflectivity of about 45% or less.

[0009] The method for limiting access to data disposed on the datastorage media, comprises: directing a light toward at least a portion ofthe data storage media, wherein at least a portion of the light passesthrough a UV coating, a reactive layer, and a substrate; reflecting atleast a portion of the light back through the substrate, the reactivelayer, and the UV coating; and reducing a percent reflectivity of thedata storage media to less than about 45%.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Referring now to the figures, which are meant to be illustrative,not limiting:

[0011]FIG. 1 is and isometric view of a data storage media;

[0012]FIG. 2 is a schematic showing incident light, 10, and transmittedlight, 12, passing into and being reflected from an aluminum layer in adata storage media coated with PMMA/leuco methylene blue basecoat;

[0013]FIG. 3 is a kinetics curve for conversion of leuco methylene blueto methylene blue as measured by percent reflectivity on a data storagemedia vs. time;

[0014]FIG. 4 is a graphical representation of kinetics curves forconversion of leuco methylene blue to methylene blue in PMMA with andwithout a UV cured topcoat; and

[0015]FIG. 5 is a graphical representation of reflectivity vs. time forthe Example 3 data storage media.

DETAILED DESCRIPTION OF THE INVENTION

[0016] The method for making limited-play data storage media comprises asubstrate with a reactive layer and a UV coating. Upon exposure tooxygen, a reactive material, e.g., leuco methylene blue, which isessentially colorless, is oxidized to form an opaque or semi-opaquelayer (e.g., the deep blue dye, methylene blue). Data storage media withthe opaque/semi-opaque layer can no longer be played in media players.By adjusting the time it takes to turn opaque, this method can be usedto provide limited-play data storage media having the desired life forthe given application. However, it has been found that limited-playdiscs prepared solely with the reactive material layer, in this manner,are easily “defeated”, e.g., in a bleach test, so that they are nolonger “limited-play”. The additional use of an ultra violet (UV)curable topcoat to discs with a reactive layer affords limited-play datastorage media that cannot be defeated in the bleach test.

[0017] The data storage media comprises a substrate 5 having lowbirefringence and high light transmittance at the read laser wavelength,i.e., is readable in an optical media device, a reactive materialreactive layer 3, a UV coating 1, a data storage layer 9, and areflective layer 7. (See FIGS. 1 and 2) The substrate 5 can comprisematerial having sufficient optical clarity, e.g., a birefringence ofabout ±100 nm or less, to render the data storage material readable in amedia device. Generally, polycarbonates are employed. In theory, anyplastic that exhibits these properties can be employed as the substrate.However, the plastic should be capable of withstanding the subsequentprocessing parameters (e.g., application of subsequent layers) such assputtering temperatures of about room temperature (about 25° C.) up toabout 150° C., and subsequent storage conditions (e.g., in a hot carhaving temperatures up to about 70° C.). That is, it is desirable forthe plastic to have sufficient thermal stability to prevent deformationduring the various layer deposition steps as well as during storage bythe end-user. Possible plastics include thermoplastics with glasstransition temperatures of about 100° C. or greater, with about 125° C.or greater preferred, about 150° C. or greater more preferred, and about200° C. or greater even more preferred (e.g., polyetherimides,polyetheretherketones, polysulfones, polyethersulfones,polyetherethersulfones, polyphenylene ethers, polyimides,polycarbonates, etc.); with materials having glass transitiontemperatures greater than about 250° C. more preferred, such aspolyetherimide in which sulfonedianiline or oxydianiline has beensubstituted for m-phenylenediamine, among others, as well as polyimides,combinations comprising at least one of the foregoing plastics, andothers.

[0018] Some possible examples of substrate materials include, but arenot limited to, amorphous, crystalline, and semi-crystallinethermoplastic materials such as: polyvinyl chloride, polyolefins(including, but not limited to, linear and cyclic polyolefins andincluding polyethylene, chlorinated polyethylene, polypropylene, and thelike), polyesters (including, but not limited to, polyethyleneterephthalate, polybutylene terephthalate, polycyclohexylmethyleneterephthalate, and the like), polyamides, polysulfones (including, butnot limited to, hydrogenated polysulfones, and the like), polyimides,polyether imides, polyether sulfones, polyphenylene sulfides, polyetherketones, polyether ether ketones, ABS resins, polystyrenes (including,but not limited to, hydrogenated polystyrenes, syndiotactic and atacticpolystyrenes, polycyclohexyl ethylene, styrene-co-acrylonitrile,styrene-co-maleic anhydride, and the like), polybutadiene, polyacrylates(including, but not limited to, polymethylmethacrylate (PMMA), methylmethacrylate-polyimide copolymers, and the like), polyacrylonitrile,polyacetals, polycarbonates, polyphenylene ethers (including, but notlimited to, those derived from 2,6-dimethylphenol and copolymers with2,3,6-trimethylphenol, and the like), ethylene-vinyl acetate copolymers,polyvinyl acetate, liquid crystal polymers, ethylene-tetrafluoroethylenecopolymer, aromatic polyesters, polyvinyl fluoride, polyvinylidenefluoride, polyvinylidene chloride, tetrafluoroethylenes (e.g., Teflons)

[0019] As used herein, the terms “polycarbonate”, “polycarbonatecomposition”, and “composition comprising aromatic carbonate chainunits” includes compositions having structural units of the formula (I):

[0020] in which at least about 60 percent of the total number of R¹groups are aromatic organic radicals and the balance thereof arealiphatic, alicyclic, or aromatic radicals. Preferably, R¹ is anaromatic organic radical and, more preferably, a radical of the formula(II):

-A¹-Y¹-A²-  (II)

[0021] wherein each of A¹ and A² is a monocyclic divalent aryl radicaland Y¹ is a bridging radical having zero, one, or two atoms whichseparate A¹ from A². In an exemplary embodiment, one atom separates A¹from A². Illustrative, non-limiting examples of radicals of this typeare —O—, —S—, —S(O)—, —S(O₂)—, —C(O)—, methylene, cyclohexyl-methylene,2-[2,2,1]-bicycloheptylidene, ethylidene, isopropylidene,neopentylidene, cyclohexylidene, cyclopentadecylidene,cyclododecylidene, adamantylidene, and the like. In another embodiment,zero atoms separate A¹ from A², with an illustrative example beingbiphenol (OH-benzene-benzene-OH). The bridging radical Y¹ can be ahydrocarbon group or a saturated hydrocarbon group such as methylene,cyclohexylidene or isopropylidene.

[0022] Polycarbonates can be produced by the reaction of dihydroxycompounds in which only one atom separates A¹ and A². As used herein,the term “dihydroxy compound” includes, for example, bisphenol compoundshaving general formula (III) as follows:

[0023] wherein R^(a) and R^(b) each independently represent hydrogen, ahalogen atom, or a monovalent hydrocarbon group; p and q are eachindependently integers from 0 to 4; and X^(a) represents one of thegroups of formula (IV):

[0024] wherein R^(c) and R^(d) each independently represent a hydrogenatom or a monovalent linear or cyclic hydrocarbon group, and R^(e) is adivalent hydrocarbon group.

[0025] Some illustrative, non-limiting examples of suitable dihydroxycompounds include dihydric phenols and the dihydroxy-substitutedaromatic hydrocarbons such as those disclosed by name or formula(generic or specific) in U.S. Pat. No. 4,217,438,. A nonexclusive listof specific examples of the types of bisphenol compounds that may berepresented by formula (III) includes the following:1,1-bis(4-hydroxyphenyl) methane; 1,1-bis(4-hydroxyphenyl) ethane;2,2-bis(4-hydroxyphenyl) propane (hereinafter “bisphenol A” or “BPA”);2,2-bis(4-hydroxyphenyl) butane; 2,2-bis(4-hydroxyphenyl) octane;1,1-bis(4-hydroxyphenyl) propane; 1,1-bis(4-hydroxyphenyl) n-butane;bis(4-hydroxyphenyl) phenylmethane; 2,2-bis(4-hydroxy-1-methylphenyl)propane; 1,1-bis(4-hydroxy-t-butylphenyl) propane; bis(hydroxyaryl)alkanes such as 2,2-bis(4-hydroxy-3-bromophenyl) propane;1,1-bis(4-hydroxyphenyl) cyclopentane; 4,4′-biphenol; andbis(hydroxyaryl) cycloalkanes such as 1,1-bis(4-hydroxyphenyl)cyclohexane; and the like as well as combinations comprising at leastone of the foregoing bisphenol compound.

[0026] It is also possible to employ polycarbonates resulting from thepolymerization of two or more different dihydric phenols or a copolymerof a dihydric phenol with a glycol or with a hydroxy- or acid-terminatedpolyester or with a dibasic acid or with a hydroxy acid or with analiphatic diacid in the event a carbonate copolymer rather than ahomopolymer is desired for use. Generally, useful aliphatic diacids haveabout 2 to about 40 carbons. A preferred aliphatic diacid isdodecandioic acid.

[0027] Polyarylates and polyester-carbonate resins or their blends canalso be employed. Branched polycarbonates are also useful, as well asblends of linear polycarbonate and a branched polycarbonate. Thebranched polycarbonates may be prepared by adding a branching agentduring polymerization.

[0028] These branching agents are well known and may comprisepolyfunctional organic compounds containing at least three functionalgroups which may be hydroxyl, carboxyl, carboxylic anhydride,haloformyl, and mixtures comprising at least one of the foregoingbranching agents. Specific examples include trimellitic acid,trimellitic anhydride, trimellitic trichloride, tris-p-hydroxy phenylethane, isatin-bis-phenol, tris-phenol TC(1,3,5-tris((p-hydroxyphenyl)isopropyl)benzene), tris-phenol PA(4(4(1,1-bis(p-hydroxyphenyl)-ethyl) α,α-dimethyl benzyl)phenol),4-chloroformyl phthalic anhydride, trimesic acid, benzophenonetetracarboxylic acid, and the like, as well as combinations comprisingat least one of the foregoing branching agents. The branching agents maybe added at a level of about 0.05 to about 2.0 weight percent, basedupon the total weight of the substrate. Examples of branching agents andprocedures for making branched polycarbonates are described in U.S. Pat.Nos. 3,635,895 and 4,001,184. All types of polycarbonate end groups areherein contemplated.

[0029] Preferred polycarbonates are based on bisphenol A, in which eachof A¹ and A² is p-phenylene and Y¹ is isopropylidene. Preferably, theweight average molecular weight of the polycarbonate is about 5,000 toabout 100,000 atomic mass units, more preferably about 10,000 to about65,000 atomic mass units, and most preferably about 15,000 to about35,000 atomic mass units.

[0030] In monitoring and evaluating polycarbonate synthesis, it is ofparticular interest to determine the concentration of Fries productpresent in the polycarbonate. As noted, the generation of significantFries product can lead to polymer branching, resulting in uncontrollablemelt behavior. As used herein, the terms “Fries” and “Fries product”denote a repeating unit in polycarbonate having the formula (V):

[0031] wherein X^(a) is a bivalent radical as described in connectionwith Formula (III) supra.

[0032] The polycarbonate composition may also include various additivesordinarily incorporated in resin compositions of this type. Suchadditives are, for example, fillers or reinforcing agents; heatstabilizers; antioxidants; light stabilizers; plasticizers; antistaticagents; mold releasing agents; additional resins; blowing agents; andthe like, as well as combinations comprising at least one of theforegoing additives.

[0033] In order to aid in the processing of the substrate material(e.g., the production of polycarbonate via a melt process) or to controla property of the substrate material (e.g., viscosity). catalyst(s) mayalso be employed. Possible catalysts include tetraalkylammoniumhydroxide, tetraalkylphosphonium hydroxide, and the like, withdiethyldimethylammonium hydroxide, and tetrabutylphosphonium hydroxidepreferred. The catalyst(s) can be employed alone or in combination withquenchers such as acids, e.g., as phosphoric acid, and the like.Additionally, water may be injected into the polymer melt duringcompounding and removed as water vapor through a vent to remove residualvolatile compounds.

[0034] Data storage media can be produced by first forming the substratematerial using a conventional reaction vessel capable of adequatelymixing various precursors, such as a single or twin screw extruder,kneader, blender, or the like. The extruder should be maintained at asufficiently high temperature to melt the substrate material precursorswithout causing decomposition thereof. For polycarbonate, for example,temperatures of about 220° C. to about 360° C. can be used, with about260° C. to about 320° C. preferred. Similarly, the residence time in theextruder should be controlled to minimize decomposition. Residence timesof up to about 2 minutes (min) or more can be employed, with up to about1.5 min preferred, and up to about 1 min especially preferred. Prior toextrusion into the desired form (typically pellets, sheet, web, or thelike, the mixture can optionally be filtered, such as by melt filteringand/or the use of a screen pack, or the like, to remove undesirablecontaminants or decomposition products.

[0035] Once the plastic composition has been produced, it can be formedinto the substrate using various molding and/or processing techniques.Possible techniques include injection molding, film casting, extrusion,press molding, blow molding, stamping, and the like. Once the substratehas been produced, additional processing, such as electroplating,coating techniques (spin coating, spray coating, vapor deposition,screen printing, painting, dipping, and the like), lamination,sputtering, and the like, as well as combinations comprising at leastone of the foregoing processing techniques, may be employed to disposedesired layers on the substrate.

[0036] An example of a limited play polycarbonate data storage mediacomprises an injection molded polycarbonate substrate. Disposed on thesubstrate are various layers including: a data layer, dielectriclayer(s), a reactive layer(s), a UV layer(s), a reflective layer(s),and/or a protective layer, as well as combinations comprising at leastone of the foregoing layers. For an optical media, the layers may beprotective layer, reflective layer, dielectric layer, and data storagelayer, with a subsequent dielectric layer in contact with the substrateand the UV layer disposed on the opposite side of the substrate, withthe reactive layer disposed between the substrate and the UV layer. Itis understood that the form of the data storage media is not limited todisc shape, but may be any size and shape which can be accommodated in areadout device.

[0037] The data storage layer(s) may comprise any material capable ofstoring retrievable data, such as an optical layer, magnetic layer, or amagneto-optic layer. Typically the data layer has a thickness of up toabout 600 Angstroms (Å) or so, with a thickness up to about 300 Åpreferred. Possible data storage layers include, but are not limited to,oxides (such as silicone oxide), rare earth element—transition metalalloy, nickel, cobalt, chromium, tantalum, platinum, terbium,gadolinium, iron, boron, others, and alloys and combinations comprisingat least one of the foregoing, organic dye (e.g., cyanine orphthalocyanine type dyes), and inorganic phase change compounds (e.g.,TeSeSn, InAgSb, and the like).

[0038] The protective layer(s), which protect against dust, oils, andother contaminants, can have a thickness of greater than about 100microns (μ) to less than about 10 Å, with a thickness of about 300 Å orless preferred in some embodiments, and a thickness of about 100 Å orless especially preferred. The thickness of the protective layer(s) isusually determined, at least in part, by the type of read/writemechanism employed, e.g., magnetic, optic, or magneto-optic. Possibleprotective layers include anti-corrosive materials such as gold, silver,nitrides (e.g., silicon nitrides and aluminum nitrides, among others),carbides (e.g., silicon carbide and others), oxides (e.g., silicondioxide and others), polymeric materials (e.g., polyacrylates orpolycarbonates), carbon film (diamond, diamond-like carbon, and thelike), among others, and combinations comprising at least one of theforegoing materials.

[0039] The dielectric layer(s), which are disposed on one or both sidesof the data storage layer and are often employed as heat controllers,can typically have a thickness of up to or exceeding about 1,000 Å andas low as about 200 Å or less. Possible dielectric layers includenitrides (e.g., silicon nitride, aluminum nitride, and others); oxides(e.g., aluminum oxide); carbides (e.g., silicon carbide); andcombinations comprising at least one of the foregoing materials, amongother materials compatible within the environment and preferably notreactive with the surrounding layers.

[0040] The reflective layer(s) should have a sufficient thickness toreflect a sufficient amount of energy (e.g., light) to enable dataretrieval. Typically the reflective layer(s) can have a thickness of upto about 700 Å or so, with a thickness of about 300 Å to about 600 Ågenerally preferred. Possible reflective layers include any materialcapable of reflecting the particular energy field, including metals(e.g., aluminum, silver, gold, titanium, and alloys and mixturescomprising at least one of the foregoing metals, and others).

[0041] The reactive layer, which comprises both a carrier and a reactivematerial, should initially have sufficient transmission to enable dataretrieval by the data storage media device, and subsequently form alayer which inhibits data retrieval by that device (e.g., which absorbsa sufficient amount of light i.e., incident and/or reflected light) atthe wavelength of the laser in the given device). Typically a layer thatallows an initial percent reflectivity from the reflective layer ofabout 50% or greater can be employed, with an initial percentreflectivity of about 65% or greater preferred, and an initial percentreflection of about 75% or greater more preferred. Once the media hasbeen exposed to oxygen, e.g., air, for a desired period of time (e.g.,the desired allowable play time of the media), the layer preferablycomprises a percent reflectivity of about 45% or less, with about 30% orless preferred, about 20% or less more preferred, and about 15% or lessespecially preferred.

[0042] Possible reactive materials include oxygen sensitive leuco orreduced forms of methylene blue, brilliant cresyl blue, basic blue 3,and toluidine 0, as well as reaction products and combinationscomprising at least one of the foregoing material; the structures ofwhich are set forth as formulas VI-IX below:

[0043] Another possible reactive material comprises a dye whichre-oxidizes over approximately 48 hours without a UV coating. Thesynthesis and oxidation of this dye is shown below:

[0044] The method of synthesis and the oxygen dependent reoxidation toform the colored form of the methylene blue dye is shown below:

[0045] In addition to the above reactive materials, numerous other dyesand light blocking materials, can be synthesized to operate to renderthe data storage media limited play. For example, some other possiblereactive materials can be found in U.S. Pat. No. 4,404,257 and U.S. Pat.No. 5,815,484. The reactive materials can further comprise a mixturecomprising at least one of any of the abovementioned reactive materials.

[0046] The amount of reactive material in the reactive layer isdependent upon the desired life of the data storage media in combinationwith the oxygen permeability of the UV coating. For a life of up toabout 3 days, with a 2μ to about 30μ thick UV coating, the amount ofreactive material in the reactive layer can be as little as about 0.1weight percent (wt %), with about 3 wt % preferred, and about 4 wt %more preferred, based upon the total weight of the reactive layer; withan upper amount of reactive material being about 10 wt %, with about 7wt % preferred, about 6 wt % more preferred, and about 5 wt % even morepreferred.

[0047] The reactive material is preferably mixed with a carrier fordeposition on and/or impregnation into at least a portion of the surfaceof the substrate. Possible carriers comprise the thermoplastic acrylicpolymers, polyester resins, epoxy resins, polythiolenes, UV curableorganic resins, polyurethanes, thermosettable acrylic polymers, alkyds,vinyl resins and the like, as well as combinations comprising at leastone of the foregoing carriers. Polyesters include, for example thereaction products of aliphatic dicarboxylic acids including, e.g.,fumaric or maleic acid with glycols, such as ethyleneglycol,propyleneglycol, neopentylglycol, and the like, as well as reactionproducts and mixtures comprising at least one of the foregoing.

[0048] Some epoxy resins, which can be the used as the organic resin,include monomeric, dimeric, oligomeric, or polymeric epoxy materialcontaining one or a plurality of epoxy functional groups. For example,reaction products of bis phenol-A and epichlorohydrin, or theepichlorohydrin with phenol-formaldehyde resins, and the like. Otherorganic resins can be in the form of mixtures of polyolefin andpolythiols, such as shown by Kehr et al, U.S. Pat. Nos. 3,697,395 and3,697,402.

[0049] Exemplary thermoplastic acrylic polymers are set forth, forexample, in Encyclopedia of Polymer Science and Technology, Vol. 1,Interscience Publishers, John Wiley & Sons, Inc., 1964, at pp. 246 etseq. and the references cited therein, and the like, as well ascombinations comprising at least one of the foregoing polymers.

[0050] The term thermoplastic acrylic polymers, as used herein, is meantto embrace within its scope those thermoplastic polymers resulting fromthe polymerization of one or more acrylic acid ester monomers, as wellas methacrylic acid ester monomers. These monomers are represented bythe general formula X:

CH₂═CYCOOR₅  (X)

[0051] wherein Y is hydrogen or a methyl radical and R₅ is an alkylradical, preferably an alkyl radical comprising 1 to about 20 carbonatoms. Some nonlimiting examples of alkyl groups represented by R₅include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl,sec-butyl, tert-butyl, pentyl, isopentyl, hexyl, and the like.

[0052] Some nonlimiting examples of acrylic acid ester monomersrepresented by formula X include: methyl acrylate, isopropyl acrylate,n-propyl acrylate, n-butyl acrylate, isobutyl acrylate, 2-ethylhexylacrylate, and the like. Some nonlimiting examples of methacrylic acidester monomers represented by formula X include: methyl methacrylate,ethyl methacrylate, butyl methacrylate, hexyl methacrylate, isobutylmethacrylate, propyl methacrylate, and the like, as well as reactionproducts and combinations comprising at least one of the foregoing; withpoly(methyl methacrylate) (PMMA) preferred.

[0053] Copolymers of the above acrylate and methacrylate monomers arealso included within the term thermoplastic acrylic polymers as itappears herein. The polymerization of the monomeric acrylic acid estersand methacrylic acid esters to provide the thermoplastic acrylicpolymers may be accomplished by any of the known polymerizationtechniques. The thermoplastic acrylic polymers having a weight averagemolecular weight of about 30,000 g/mol or greater are generallypreferred.

[0054] In order to enhance adhesion of the reactive layer to thesubstrate, a primer may be employed therebetween. The thermoplasticacrylic polymers useful as primers include: acrylic homopolymers derivedfrom a single type of acrylic acid ester monomer; methacrylichomopolymers derived from a single type of methacrylic acid estermonomer; copolymers derived from two or more different acrylic acidester monomers, two or more different methacrylic acid ester monomers,or an acrylic acid ester monomer and a methacrylic acid ester monomer;and the like, as well as combinations comprising at least one of theforegoing primers.

[0055] Mixtures of two or more of the aforedescribed thermoplasticacrylic polymers, e.g., two or more different acrylic homopolymers, twoor more different acrylic copolymers, two or more different methacrylichomopolymers, two or more different methacrylic copolymers, an acrylichomopolymer and a methacrylic homopolymer, an acrylic copolymer and amethacrylic copolymer, an acrylic homopolymer and a methacryliccopolymer, and an acrylic copolymer and a methacrylic homopolymer, andreaction products thereof, can also be used.

[0056] Optionally, the reactive layer can be applied to the substrateusing various coating techniques such as painting, dipping, spraying,spin coating, screen printing, and the like. For example, the reactivelayer can be mixed with a relatively volatile solvent, preferably anorganic solvent, which is substantially inert towards the polycarbonate,i.e., will not attack and adversely affect the polycarbonate, but whichis capable of dissolving the carrier. Generally the concentration of thecarrier in the solvent is about 0.5 weight percent (wt %) or greater,with about 1 wt % or greater preferred, while the upper range of thepolymer is about 25 wt %, with about 15 wt % preferred. Examples of somesuitable organic solvents include ethylene glycol diacetate,butoxyethanol, the lower alkanols, and the like.

[0057] The reactive layer may also optionally contain various additivessuch as flatting agents, surface active agents, thixotropic agents, andthe like, and reaction products and combinations comprising at least oneof the foregoing additives.

[0058] The thickness of the reactive layer is dependent upon theparticular reactive material employed, the concentration thereof in thereactive layer, and the desired absorption characteristics of the layerboth initially and after a desired period of time. The reactive layercan have a thickness as low as about 0.1 microns (μ), with about 0.5μpreferred, and about 0.75μ more preferred. On the upper end, thethickness can be up to about 50μ or greater, with up to about 25μpreferred, and up to about 15μ more preferred. For example, in order toattain an initial percent reflectivity through the reactive layer ofabout 50% or greater and a percent reflectivity of about 30% or lessafter 24 hours, the layer preferably has a thickness of about 1μ toabout 25μ, with about 1.5μ to about 10μ microns more preferred.

[0059] The protective coating, which is dispersed on or impregnated intoat least a portion of the reactive layer, can comprise any UV curablematerial which is capable of forming a layer penetrable by oxygen andwhich does not substantially interfere with the transfer of lightthrough the media from and to the data retrieval device (e.g., that issubstantially transparent at the wavelength of light utilized by thedevice, and/or which allows a reflectivity from the media of about 50%or greater, with a percent reflectivity of about 65% or greaterpreferred and a percent reflectivity of about 75% or greater morepreferred). Possible UV curable materials include acrylates (e.g.,thermal cross-linked acrylates, and the like) silicon hardcoats, and thelike, as well as reaction products and combinations comprising at leastone of the foregoing materials. Other examples of UV materials aredescribed in U.S. Pat. Nos. 4,179,548 and 4,491,508. Some usefulpolyfunctional acrylate monomers include, for example, diacrylates ofthe formulas, collectively designated XI:

[0060] Although the UV coating may contain only one of saidpolyfunctional acrylate monomers, or a mixture comprising at least oneof the polyfunctional acrylate monomers (and the UV light reactionproduct thereof), preferred coating compositions contain a mixture oftwo polyfunctional monomers (and the UV light reaction product thereof),preferably a diacrylate and a triacrylate (and UV light the reactionproduct thereof), with minor amounts of mono-acrylate used in particularinstances. Optionally, the UV coating can comprise nonacrylic UV curablealiphatically unsaturated organic monomers in amounts up to about 50 wt% of the uncured UV coating that includes, for example, such materialsas N-vinyl pyrrolidone, styrene, and the like, and reaction products andcombinations comprising at least one of the foregoing materials.

[0061] When the UV layer comprises a mixture of acrylate monomers, it ispreferred that the ratio, by weight, of the diacrylate to thetriacrylate be about 10/90 to about 90/10. Exemplary mixtures ofdiacrylate and triacrylates include mixtures of hexanediol diacrylatewith pentaerythritol triacrylate, hexanediol diacrylate withtrimethylolpropane triacrylate, diethyleneglycol diacrylate withpentaerythritol triacrylate, and diethyleneglycol diacrylate withtrimethylolpropane triacrylate, and the like.

[0062] The UV coating can also comprise a photosensitizing amount ofphotoinitiator, i.e., an amount effective to effect the photocure of theUV coating in a non-oxidizing atmosphere, for example, nitrogen.Generally, this amount comprises about 0.01 wt %, with about 0.1 wt %preferred, to about 10 wt %, with about 5 wt % preferred, based upon thetotal weight of the UV coating. Possible photoinitiators include blendsof ketone-type and hindered amine type materials that form suitable hardcoatings upon exposure to UV radiation. It is preferable that the ratio,by weight, of the ketone compound to the hindered amine compound beabout 80/20 to about 20/80. Ordinarily, about 50/50 or about 60/40mixtures are quite satisfactory.

[0063] Other possible ketone-type photoinitiators, which preferably areused in a nonoxidizing atmosphere, such as nitrogen, include:benzophenone, and other acetophenones, benzil, benzaldehyde and0-chlorobenzaldehyde, xanthone, thioxanthone, 2-clorothioxanthone,9,10-phenanthrenenquinone, 9,10-anthraquinone, methylbenzoin ether,ethylbenzoin ether, isopropyl benzoin ether, α,α-diethoxyacetophenone,α,α-dimethoxyacetophenone, 1-phenyl-1,2-propanediol-2-o-benzoyl oxime,α,α-dimethoxy-α-phenylacetopheone, phosphine oxides, and the like.Further included are reaction products and combinations comprising atleast one of the foregoing photoinitiators.

[0064] The UV layer may also optionally comprise flatting agents,surface active agents, thixotropic agents, UV light stabilizers, UVabsorbers and/or stabilizers such as resorcinol monobenzoate, 2-methylresorcinol dibenzoate, and the like, as well as combinations reactionproducts comprising at least one of the foregoing. The stabilizers canbe present in an amount, based upon the weight of the uncured UV layerof about 0.1 wt %, preferably about 3 wt %, to about 15 wt %.

[0065] Having met the defeatability test, limited-play data storagemedia with a reactive layer (e.g., poly (methyl methacrylate)/leucomethylene blue basecoat) and a UV cured topcoat were tested forplayability. Upon initial exposure to oxygen, the disc was playable.During longer exposure to oxygen, the disc gradually turned blue as theleuco methylene blue was oxidized and ultimately became non-playable.This was surprising since nearly all UV cured acrylic resins arecrosslinked materials, and a variety of cross linked materials are knownto be barriers to oxygen, and since the protective layer could be UVcured without causing the reactive layer to oxidize prematurely. Forexample, transparent barrier coatings applied by electron beamevaporation have recently been reviewed (ref: Proceedings, AnnualTechnical Conference—Society of Vacuum Coaters 1998, Soc. of VacuumCoaters, Albuquerque, N. Mex., USA. p. 424-428). If oxygen could notdiffuse through the UV topcoat to the leuco methylene blue in thereactive layer, oxidation of the leuco methylene blue would not occur toform methylene blue which is required for limited playability, asdescribed above.

[0066] A second benefit of having a UV cured topcoat was discovered, asfollows. The rate of oxidation of the leuco methylene blue to methyleneblue was determined by measuring the percent reflectivity of coateddiscs. The percent reflectivity is related to the amount of incidentlight, arrow 10, that is absorbed in passing through several layers,including a PMMA/leuco methylene blue layer, as shown in FIG. 2. Thepercent reflectivity is the ratio of transmitted light, arrow 12, toincident light.

[0067] As more methylene blue is formed by oxidation of leuco methyleneblue, the amount of light reflected from the aluminum surface in a datastorage media is reduced since the methylene blue that is formed absorbssome of the incident and reflected light. A typical kinetics curveresult is shown in FIG. 3 for a PMMA/leuco methylene blue coating on adata storage media.

[0068] Ideally for a limited-play data storage media, it would bedesirable to have no loss of percent reflectivity for a period of timeso that the limited-play data storage media would play impeccably inevery type of data storage media player Alternatively, having a veryhigh percent reflectivity (e.g., an initial percent reflectivity ofabout 75% or greater), with a maintained percent reflectivity of about65% or greater for the desired period of time, meets the most customerrequirements. As shown in FIG. 3 above, percent reflectivity fallsimmediately as leuco methylene blue in PMMA is exposed to air.

[0069] Surprisingly it has been found that when a UV topcoat is appliedto a PMMA/lecuo methylene blue basecoat, the time is extended before thepercent reflectivity begins to fall relative to a basecoat that has notopcoat, shown below. Thus high reflectivity is maintained longer sothat playability in a data storage media player can be guaranteed for alonger period of time. Specifically, it has been found that some typesof data storage media players do not play data storage media when thepercent reflectivity is 45% or less. In FIG. 4, it can be seen that whenthere is no UV topcoat on the PMMA/leuco methylene blue basecoat, thepercent reflectivity reaches 45% in about 1 to about 2 hours whereas ittakes about 4 to about 8 hours when a UV topcoat is present.

EXAMPLES Example 1

[0070] This example describes preparation of PMMA/leuco methylene bluecoating solution.

[0071] A solution of PMMA in 1-methoxy-2propanol was prepared by adding60 grams of Elvacite 2010 poly (methyl methacrylate) from Ineos Acrylicsto 300 grams of 1-methoxy-2propanol in a bottle and rolling on a rollermill to effect dissolution. The solution was transferred to a flask andheated to about 80° C. while a slow stream of nitrogen was passed overthe surface of the solution. The de-aerated solution was transferredusing nitrogen pressure to a de-aerated bottle closed with a rubberseptum using a cannula tube.

[0072] A leuco methylene blue solution was prepared by combining 1.2grams of methylene blue trihydrate and 0.80 grams of camphor sulfonicacid with 40 grams of 1-methoxy-2propanol in a 100-mL flask equippedwith a rubber septum. The stirred mixture was heated in a 90° C. waterbath while a stream of nitrogen was passed into the flask using syringeneedles for both the nitrogen inlet and outlet. While hot, 4.2milliliters (mL) of tin (II) 2-ethylhexanoate was added by syringe toreduce the methylene blue to the dark amber leuco methylene blue. To thesolution was added 0.6 mL of polyether modified poly-dimethyl-siloxane.

[0073] To make the PMMA/leuco methylene blue coating solution, the leucomethylene blue solution above was drawn into a syringe and then injectedinto the PMMA solution after having been passed through a 0.2-micronsyringe filter.

Example 2

[0074] This example illustrates the preparation of a disc with thePMMA//leuco methylene blue layer. Approximately 3 mL of the Example 1PMMA/leuco methylene blue coating solution was applied as a ring aroundthe inner diameter of a DVD held on a spin coater. After spin coating at500 rpm for 60 seconds, the coating was tack-free and essentiallycolorless (e.g., a percent reflectivity of about 65%). The disc wasplaced a DVD player and was completely playable.

Example 3

[0075] The coated disc from Example 2 was allowed to stand at ambientroom conditions during which time average percent reflectivity wasmeasured at various times using a Dr. Schenk PROmeteus MT-136E opticaldisk tester. As the percent reflectivity dropped the color of the discturned from essentially colorless to blue. After the disc had been inair for about 1 week, it was very blue and would not play in a DVDplayer; e.g., the disc had a percent reflectivity of about 10%.

Example 4

[0076] This example illustrates that the disc described in Examples 2and 3 is defeatable. The blue disc from Example 3 was placed in asolution of 3 parts by weight of household bleach and 7 parts by weightof water. After standing in this solution overnight, the disc was againcolorless (i.e., a percent reflectivity of greater than about 50%) andthe coating appeared to have been removed. Another disc prepared in thesame fashion as the one in Example 2 was placed in a closed containerabove a bleach solution. After standing overnight, the blue color in thePMMA coating was gone. Both discs were completely playable in a DVDplayer.

Example 5

[0077] This example illustrates preparation of a PMMA/leuco methyleneblue layer and UV coated DVD disc. A solution was prepared as in Example1 except the following quantitites of raw materials were used. Note:Elvacite 2008 is a low molecular weight version of poly (methylmethacrylate). grams PMMA Solution Dowanol 579.0 Total Elvacite 157.5Elvacite 2008: 118.1 Elvacite 2010: 39.4 Dye Solution methylene blue8.09 trihydrate camphorsulfonic acid 3.02 Dowanol PM 161.21 stannousoctanoate 18.74 BYK-301 1.58

[0078] The solution was used to apply a PMMA/leuco methylene bluebasecoat to a DVD the same as in Example 2 except the discs were spun at500 rpm for 3 seconds and then at 1,000 rpm for 7 seconds. The averagecoating thickness was 2.6 microns.

[0079] After one of the discs with the PMMA/leuco methylene bluebasecoat had been stored overnight in a nitrogen chamber, UV resin, amixture of acrylates commonly known as Daicure SD-640 (commerciallyavailable from DaiNippon, Inc., and Dic Trading, USA, Fort Lee, N.J.)was applied to it in the manner described in Example 2, spun at 1,000rpm for 3 seconds, and passed under a UV lamp.

[0080] The kinetics of oxidation of a disc with just the basecoat andthat of another with the UV topcoat on the basecoat were determined inthe manner of Example 3. The results are shown in FIG. 4.

Example 6

[0081] The two discs from Example 5 were subjected to the bleach testsdescribed in Example 4. The disc with just the basecoat failed thebleach test just like the disc in Example 4. However, the disc with theUV topcoat did not lose its blue color when immersed in bleach or whenit was exposed to bleach vapors. In addition, it was not playable in aDVD player. This illustrates that the coated DVD with the UV coatingpasses the bleach defeatability test.

[0082] The use of a UV coating in combination with a reactive materialcan be used to make a variety of limited-use optical media devices byadjusting the thickness/density of the UV coating, the period ofplayability of the disc can be adjusted as desired.

[0083] While preferred embodiments have been shown and described,various modifications and substitutions may be made thereto withoutdeparting from the spirit and scope of the invention. Accordingly, it isto be understood that the present invention has been described by way ofillustration only, and such illustrations and embodiments as have beendisclosed herein are not to be construed as limiting to the claims.

1. A limited play optical storage media, comprising: an opticallytransparent substrate; a reflective layer; an oxygen penetrable UVcoating disposed on a side of said substrate opposite said reflectivelayer; and a reactive layer disposed between said UV coating and saidsubstrate, said optical storage media having an initial percentreflectivity of about 50% or greater and a subsequent percentreflectivity of about 45% or less.
 2. A limited play optical storagemedia as in claim 1, wherein said substrate comprises polycarbonateproduced from a bis(hydroxyaryl) cycloalkane.
 3. A limited play opticalstorage media as in claim 2, wherein said bis(hydroxyaryl) cycloalkanecomprises 1,1-bis(4-hydroxyphenyl) cyclohexane.
 4. A limited playoptical storage media as in claim 1, wherein said substrate comprises athermoplastic having a glass transition temperature of about 100° C. orgreater.
 5. A limited play optical storage media as in claim 1, whereinsaid substrate is selected from the group consisting of polyimides,polyacrylates, polycarbonates, polyphenylene ethers, and mixtures,copolymers, reaction products, and composites comprising at least one ofthe foregoing thermoplastics.
 6. A limited play optical storage media asin claim 5, wherein the substrate is selected from the group consistingof polycarbonates, polyacrylates, and copolymers and combinationscomprising at least one of the foregoing.
 7. A limited play opticalstorage media as in claim 1, wherein the substrate is selected from thegroup consisting of polyphenylene ether, polystyrene, and copolymers andcombinations comprising polyphenylene ether and polystyrene.
 8. Alimited play optical storage media as in claim 1, wherein said UVcoating is selected from the group consisting of acrylates, siliconhardcoats, nonacrylic UV curable aliphatically unsaturated organicmonomers, and reaction products and combinations comprising at least oneof the foregoing UV coatings.
 9. A limited play optical storage media asin claim 8, wherein said UV coating comprises thermal cross-linkedacrylates.
 10. A limited play optical storage media as in claim 8,wherein said UV coating comprises diacrylate, a triacrylate, N-vinylpyrrolidone, styrene, and reaction products and combinations comprisingat least one of the foregoing UV coatings.
 11. A limited play opticalstorage media as in claim 8, wherein said reactive layer furthercomprises polymethylmethacrylate/leuco methylene blue.
 12. A limitedplay optical storage media as in claim 1, wherein said reactive layerfurther comprises a reactive material selected from the group consistingof oxygen sensitive leuco methylene blue, reduced forms of methyleneblue, brilliant cresyl blue, basic blue 3, toluidine 0, and combinationscomprising at least one of the foregoing reactive materials.
 13. Alimited play optical storage media as in claim 1, wherein said reactivelayer further comprises about 0.1 wt % to about 10 wt % reactivematerial, based upon a total weight of said reactive layer.
 14. Alimited play optical storage media as in claim 13, wherein said reactivelayer further comprises about 3 wt % to about 7 wt % reactive material,based upon a total weight of said reactive layer.
 15. A limited playoptical storage media as in claim 14, wherein said reactive layerfurther comprises about 4 wt % to about 6 wt % reactive material, basedupon a total weight of said reactive layer.
 16. A limited play opticalstorage media as in claim 1, wherein said reactive layer furthercomprises a carrier selected from the group consisting of thermoplasticacrylic polymers, polyester resins, epoxy resins, polythiolenes, UVcurable organic resins, polyurethanes, thermosettable acrylic polymers,alkyds, vinyl resins, and reaction products and combinations comprisingat least one of the foregoing carriers.
 17. A limited play opticalstorage media as in claim 16, wherein said carrier is selected from thegroup consisting of reaction products of aliphatic dicarboxylic acids;monomeric, dimeric, oligomeric or polymeric epoxy material comprising atleast one epoxy functional group; polyolefins, polythiols, andcombinations comprising at least one of the foregoing carriers.
 18. Alimited play optical storage media as in claim 17, wherein said carrieris selected from the group consisting of ethyleneglycol;propyleneglycol; neopentylglycol; reaction products of bis phenol-A andepichlorohydrin; reaction products of epichlorohydrin withphenol-formaldehyde resins; acrylic acid ester monomers; andcombinations comprising at least one of the foregoing carriers.
 19. Alimited play optical storage media as in claim 1, wherein saidsubsequent percent reflectivity is about 30% or less.
 20. A limited playoptical storage media as in claim 1, wherein said subsequent percentreflectivity is about 20% or less.
 21. A limited play optical storagemedia as in claim 1, wherein said subsequent percent reflectivityremains at 45% or less even if said optical storage media is exposed tobleach.
 22. A limited play optical storage media as in claim 1, furthercomprising a data storage layer disposed between disposed between saidsubstrate and said reflective layer, wherein said data storage layercomprises an organic dye.
 23. A limited play optical storage media as inclaim 1, further comprising a data storage layer disposed betweendisposed between said substrate and said reflective layer, wherein saiddata storage layer comprises inorganic phase change compound.
 24. Alimited play optical storage media as in claim 1, further comprising adata storage layer disposed between disposed between said substrate andsaid reflective layer, wherein said data storage layer comprises amaterial selected from the group consisting of rare earthelement—transition metal alloy, nickel, cobalt, chromium, tantalum,platinum, terbium, gadolinium, iron, boron, and alloys and combinationscomprising at least one of the foregoing materials.
 25. A limited playoptical storage media, comprising: an optically transparent substrate; areflective layer; an oxygen penetrable UV coating disposed on a side ofsaid substrate opposite said reflective layer, wherein said UV coatingallows a reflectivity from said optical storage media of about 50% orgreater; and a reactive layer disposed between said UV coating and saidsubstrate, said optical storage media having an initial percentreflectivity of about 50%, said reactive layer comprisingpolymethylmethacrylate/leuco methylene blue.
 26. A method for limitingaccess to data disposed on a data storage media, comprising: directing alight toward at least a portion of said data storage media, wherein atleast a portion of said light passes through a UV coating, a reactivelayer, and a substrate; reflecting at least a portion of said light backthrough said substrate, said reactive layer, and said UV coating; andreducing a percent reflectivity of said data storage media to less thanabout 45%.
 27. A method for limiting access to data disposed on a datastorage media as in claim 26, wherein said percent reflectivity is about30% or less.
 28. A method for limiting access to data disposed on a datastorage media as in claim 27, wherein said percent reflectivity is about20% or less.
 29. A method for limiting access to data disposed on a datastorage media as in claim 28, wherein said percent reflectivity is about15% or less.
 30. A method for limiting access to data disposed on a datastorage media as in claim 26, wherein said reactive layer furthercomprises polymethylmethacrylate/leuco methylene blue.
 31. A method forlimiting access to data disposed on a data storage media as in claim 26,wherein said reactive layer further comprises about 0.1 wt % to about 10wt % reactive material, based upon a total weight of said reactivelayer.
 32. A method for limiting access to data disposed on a datastorage media as in claim 31, wherein said reactive layer furthercomprises about 3 wt % to about 7 wt % reactive material, based upon atotal weight of said reactive layer.